Effect of environmental pollution by some pesticides on the mortality rate and behaviour of the Nile bolti, tilapia nilotica

ABSTRACT

Adult Tilapia nilotica were exposed to water containing different concentrations of three types of insecticides pollutants including methomyl, cypermethrin and malathion. These pollutants are currently used and contaminate the Egyptian waterways. Survival and behaviour were the responses used for measuring the toxic effects. The data indicate that the mortality rate increased with the increase of toxic dose and exposure time and therefore, the survival percentage decreased with the increase of insecticide concentration. The order of toxicity of the three used pesticides is arranged in a descending manner as methomyl, cypermethrin and malathion repectively. From the TLm measurements, the 24 h. LC[50] in Tilapia nilotica was 0.16, 0.58 and 0.80 mg.l[-1] for methomy1, cypermethrin and malathion respectively. The behaviour pattern of the toxicant fishes was found to be in the form of hyperexcitation followed by a state of unbalance and a reduction in activity till death occurred